ABSTRACT Adolescence is a critical developmental time period in which experimentation with marijuana is common. Marijuana use in adolescence is associated with negative health consequences including effects on cognitive development and increased injury risks. The legalization of adult recreational marijuana use will affect adolescents even though there are legal limitations on their ability to purchase marijuana in stores. Teens are now exposed to recreational marijuana promotions through social media such as Facebook and Twitter, and traditional advertisements (ads) such as billboards along major roadways. Previous research on tobacco and alcohol illustrate that advertising contributes to adolescents? initiation of these substances. Marijuana promotions present several new public health challenges such as focused efforts in the social media space, which include providing messages linking marijuana to positive health outcomes and influencing norms around marijuana use. At present, critical unanswered questions include: 1) the reach of marijuana promotions and ads to adolescents in a state where recreational marijuana is legal, 2) strategies that marijuana promotions and ads use to influence consumers and target youth, and 3) how adolescents interpret these marijuana promotions and ads. Now is a critical time to understand marijuana promotions and ads while policies that regulate them are nascent or emerging. Our over-arching goal is to address these critical gaps in the literature towards informing theory, policy and future interventions. This proposal includes three linked aims towards this goal. Our conceptual approach will be the Theory of Normative Social Behavior (TNSB) which supports the role of injunctive norms in predicting behavior. Aim 1: We will conduct a cross-sectional survey of adolescents in the Seattle metro area (n=500) to determine the local reach of marijuana promotions and ads in a state where recreational marijuana is legalized. We will determine risk factors for exposure to marijuana promotions and ads, and investigate associations between marijuana promotion/ad exposure and intention to use marijuana mediated by TNSB constructs. Aim 2: We will conduct a content analysis of one year of recreational marijuana promotions on social media (estimated 20,000 posts) and ads including billboard and print applying TNSB constructs. Aim 3: We will work with adolescents (n=160) as stakeholders to develop a concept map representing key concepts in how marijuana promotions and ads exert influence. We will determine how the concepts in this stakeholder-driven concept map are similar or different to those represented in tobacco and alcohol ads, and compare these key influential concepts to those in existing health behavior theory such as TNSB. This proposal is consistent with the research goals outlined in PAS-14-020: Public Health Impact of the Changing Policy/Legal Environment for Marijuana. Our study team includes investigators with expertise in social media, adolescent health, advertisements and marijuana. The outcomes of this ambitious and comprehensive study will inform theory, policy and interventions to prevent marijuana use among adolescents.